1304 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1953 



collector and emitter potentials in that order, while the last three are 

 ac terms resulting from collector potential, emitter potential, and base 

 layer thickness variation respectively. 



The hole-current densities may be related to the ac potentials by use 

 by use of the approximations given at the beginning of paragraph 1.3. 



Pel ^ VeO ^ Vel Pel ^ PcO ^ Fel 



and the relation 



dw T, 



However, the average collector potential Vco is negative and many times 

 kT/q so that pco c^ and pci = 0. The ac emitter hole-current density 

 is therefore 



IpeiC'''' = ?^ (Vel ^ SpeO COth (sWo/L) 



- -j^ , J- s csch iswo/L)[(pei - pn) csch {Wq/L) 



- {qcQ - Pn) COth {wQ/L)])e'"* 

 If peo > Pn , equations (13a) and (13b) becomes very closely 



pel 



r q s tanh (wp/L) ^^ dw sVd 1 ..^m 



I''' kT tanh (swo/L) ^ '' "^ ^''' dVe' L sinh (swo/L)] ^'"^^^ 



In equation (13b), Ipeo and Ipco are average emitter and collector 

 hole-current densities. The entire coefficients of Vei and Vd in equation 

 (13b) are the input and the feedback short-circuit admittances associ- 

 ated with hole flow in the transistor. 



Similarly, forward transfer and output short-circuit admittances as- 

 sociated with hole flow may be found from equation (12) by stubstitu- 

 tion oi X = Wq and use of the approximation pi ^:^ pi — Pn , i.e., pi ^ 

 Pn . In calculating collector current, the sign of equation (12) must be 

 reversed, since equation (12) gives current flow in the x-direction while 

 collector current is assumed to flow in the negative a:-direction. The 

 admittances are given in the summary at the end. 



Next, there are admittances associated with electron flow in the 

 p-n-p transistor. Flow of electrons from base to emitter gives rise to an 

 input admittance term, while electrons flowing from collector to base 

 give rise to output and forward transfer admittance terms. An outline 



